Vehicle-oriented satellite navigation systems are all the rage, as they allow drivers to search maps, plan itineraries, and perform real-time locating. To enable drivers on roads to access real-time coverage of road conditions and weather, vehicle-oriented satellite navigation systems nowadays are equipped with a built-in receiving module for use with Traffic Message Channel (TMC). TMC is a communication application in real-time coverage of traffic and weather, and is effective in providing real-time coverage of traffic and weather by radio communication technology as well as enhancing the real-time characteristic and accuracy in prediction of road conditions by a navigation device. The navigation device operates in conjunction with a TMC receiving apparatus and makes good use of related information and drawings so as to inform, by voice, graphic, or text, users of related real-time information. Among the ways of transmitting messages by TMC, the commonest is FM subcarrier TMC which has the widest use in Europe nowadays.
To enable the aforesaid vehicle-oriented satellite navigation systems to receive TMC radio waves, related prior art teaches an antenna as shown in FIG. 1. The antenna essentially comprises a uniaxial wire 10 of a length equal to a fourth of the wavelength of radio waves intended to be received and transmitted at intended frequencies (a single frequency domain). Hence, to receive radio waves of two frequency domains, such as 76 MHz˜90 MHz (Japan) and 88 MHz˜108 MHz (Taiwan), the uniaxial wire 10 has to be series-connected to another uniaxial wire operable at another wavelength. However, a series-connected antenna structure causes the narrowing of a bandwidth and prevents the optimization of the voltage standing wave ratio (VSWR).
Accordingly, it is imperative to invent an antenna capable of overcoming the aforesaid drawbacks of the prior art.